A firewall is a system designed to prevent unauthorized access to or from a private network (which could be just one machine). Firewalls can be implemented in only hardware or software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and allows, proxys, or denies the traffic based on specified security criteria.

There are many posts on the forums about different firewall apps and scripts so here they all are condensed into one page - please add your comments about each firewall, especially ease of use and a security check at Shields Up.

Note: Checks at Shields Up are only a valid measure of your router should you have one in the LAN. To accurately evaluate a software firewall, one needs to directly connect the box to the cable modem.

ferm

ferm (which stands for "For Easy Rule Making") is a tool to maintain complex firewalls, without having the trouble to rewrite the complex rules over and over again. ferm allows the entire firewall rule set to be stored in a separate file, and to be loaded with one command. The firewall configuration resembles structured programming-like language, which can contain levels and lists.

Firehol

FireHOL is a language to express firewalling rules, not just a script that produces some kind of a firewall. It makes building even sophisticated firewalls easy - the way you want it. The result is actually iptables rules.

Firetable

gShield

gShield is a really simple iptables configuration system. (Nothing to do with gnome) Easy to configure, blocks everything not needed (almost) by default. Controlled by only one configuration file. It gave me all stealth on grc.com

Shorewall

The Shoreline Firewall, more commonly known as "Shorewall", is high-level tool for configuring Netfilter. You describe your firewall/gateway requirements using entries in a set of configuration files. Shorewall reads those configuration files and with the help of the iptables utility, Shorewall configures Netfilter to match your requirements. Shorewall can be used on a dedicated firewall system, a multi-function gateway/router/server or on a standalone GNU/Linux system. Shorewall does not use Netfilter's ipchains compatibility mode and can thus take advantage of Netfilter's connection state tracking capabilities.

uruk

uruk loads an rc file, which defines network service access policy, and invokes iptables to set up firewall rules implementing this policy.

uruk is not available in any Arch Linux repository.

ufw

ufw (uncomplicated firewall) is a simple frontend for iptables and is available in [community]. The next two sections are simply high-level explanations and examples. Users are encouraged to consult the Ubuntu Firewall Help page for additional details.

Basic Configuration

A very simplistic configuration which will deny all by default, allow any protocol from inside a 192.168.0.1-192.168.0.255 LAN, and allow incoming Deluge and SSH traffic from anywhere:

Adding Other Applications

The PKG comes with some defaults based on the default ports of many common daemons and programs. Inspect the options by looking in the /etc/ufw/applications.d directory or by listing them in the program itself:

# ufw app list

If users are running any of the applications on a non-standard port, it is recommended to simply make Template:Filename containing the needed data using the defaults as a guide.

Warning: If users modify any of the PKG provided rule sets, these will be overwritten the first time the ufw package is updated. This is why custom app definitions need to reside in a non-PKG file as recommended above!

Vuurmuur

Vuurmuur Vuurmuur is a powerful firewall manager built on top of iptables. It has a simple and easy to learn configuration that allows both simple and complex configurations. The configuration can be fully configured through an ncurses GUI, which allows secure remote administration through SSH or on the console. Vuurmuur supports traffic shaping, has powerful monitoring features, which allow the administrator to look at the logs, connections and bandwidth usage in realtime.

iptables GUIs

Firestarter

Firestarter is a good GUI for iptables writen on GTK2, it has the ability to use both white and black lists for regulating traffic, it is very simple and easy to use, with good documentation available on their website.

Gufw

Gufw is an easy, intuitive, way to manage your Linux firewall. It supports common tasks such as allowing or blocking pre-configured, common p2p, or individual ports port(s), and many others! Gufw is powered by ufw , runs on Ubuntu, and anywhere else Python, GTK, and Ufw are available.

kcm-ufw

kcm-ufw is KDE4 control module for ufw. The following features are supported: